Wearable Spiral Antenna Coplanar Waveguide Feed
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Developing a wearable antenna that is both undetectable and robust enough to withstand normal movement and handling, while maintaining efficient radiation/reception patterns and compatibility with broadband operation, is challenging due to the need for impedance matching and the effect of variable proximity to the body.
Innovation Solution
A spiral antenna assembly with a coplanar waveguide feed structure that eliminates the need for a separate balun, using a design with slots and a line conductor in a coplanar ground plane, which provides impedance matching and is integrated with a quarter wave impedance transformer, allowing for flexible and robust construction suitable for wearable fabrics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate balun structure is used to convert unbalanced radio output to balanced antenna feed, then impedance matching is improved, but the antenna becomes easily detectable
Solution Approach 1:
The patent merges the balun function with one of the spiral arms by constructing it as a coplanar waveguide. This integration eliminates the need for a separate balun structure while maintaining the impedance transformation function, thereby reducing detectability without sacrificing impedance matching performance.
Solution Approach 2:
One spiral arm serves multiple functions: it acts as both a radiating element and an impedance transformation structure (balun). The coplanar waveguide construction enables this multi-functionality, allowing the same structure to both radiate and perform impedance matching, thus eliminating additional detectable components.
2Reliability
If traditional transmission line plus balun configuration is used, then balanced feed is achieved, but device complexity increases
Solution Approach 1:
The patent combines the transmission line and balun functions into a single coplanar waveguide structure that forms part of the spiral arm. This merging reduces the number of separate components and simplifies the overall feed structure while maintaining balanced feed capability.
Solution Approach 2:
The coplanar waveguide structure serves itself by providing both transmission and impedance transformation functions within a single configuration. The structure automatically provides balanced feed without requiring additional external balun components, achieving self-sufficiency in the feed system.
3Device complexity
If spiral antenna with infinite balun is used, then separate balun is eliminated, but significant depth is required making it very detectable
Solution Approach 1:
The patent uses a coplanar waveguide constructed on a flexible substrate that can be conformally attached to the clothing surface. This thin-film approach eliminates the need for deep three-dimensional structures while maintaining the infinite balun effect, thereby reducing detectability through the clothing material.
Solution Approach 2:
The patent transitions from a three-dimensional deep spiral structure to a two-dimensional coplanar waveguide configuration. By flattening the structure onto a thin substrate, the antenna maintains its electrical performance while minimizing physical depth and detectability through the clothing.
4Reliability
If coplanar waveguide feed structure is used, then impedance matching is provided, but manufacturing precision requirements increase
Solution Approach 1:
The patent uses adjustable geometric parameters of the coplanar waveguide (such as conductor width, slot width, and spacing) to control impedance characteristics. By varying these parameters, precise impedance matching can be achieved while maintaining manufacturing feasibility through standard fabrication processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables a wearable antenna that is difficult to detect, maintains efficient performance under varying conditions, and effectively matches impedance for reliable signal delivery, even when subjected to bending or folding, while handling power requirements of 5 Watts or more.
Implementation Method 1
The coplanar waveguide feed structure may provide one or more impedance transforming structures for matching the impedance of a signal feed line, for example from a radio source, to that of the spiral antenna.
Implementation Method 2
Spiral antennas are known which have an 'infinite balun'. These have a feed which winds into the centre of the spiral.
Data Source
AI summary
A wearable antenna assembly incorporates a coplanar waveguide feed in one of the arms of a two-arm spiral antenna. The antenna has relatively high impedance compared with the feed line from a suitable radio but the coplanar waveguide feed is simply modified to provide a quarter-wave transformer adjacent to the feed connection to the antenna and at least one further impedance transformation step on a tangential extension of the feed at the outer edge of the spiral antenna.